Anyone ever figure out the last level? It really doesn't seem possible.
If you go directly right from the source, digging and laying a belt along the way on both sides where you can, you have $660 left over (really $510 since you'll need a $100 miner and a $50 generator). Crossing the gap would cost $480 in belts alone, leaving only $30 to spare. But that only buys three supports, and you need a whole bridge.
You could just let the diamond fall to the floor below using gravity, eliminating the need to build a bridge. But you need to dig through the rock first, and then build an elevator at some point to lift it back up (which costs at least $600). I've experimented with letting the diamonds spill down a stairstep slope without using a belt (since you only need to transport one to win), but that gains you 1-2 tiles at most, and needs some (unpowered) elevators to help tip them any further.
The core problem is that the bare minimum of a miner, a generator, and enough belt to move horizontally from the source column to the goal column leaves only $640, and that's not enough to both dig through the intervening rock and lay a route that is seamless in terms of transport (let alone power).